<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
    var r ="" 
    var level = prompt("请输入层数：")
    if(isNaN(level))
    {
        console.log("请输入数字！")
    }else
    {
        level = parseInt(level)
        for(var i=1;i<=level;i++)
        {
            //处理空格
            for(var j=1;j<=level-i;j++)
            {
                r+=" "
            }
            //处理*
            for(var k=1;k<=i*2-1;k++)
            {
                r+="*"
            }
            r+="\n"

        }
        console.log(r)
    }

    </script>
</body>
</html>